The present invention relates to optical elements comprising fluorochemical surface treatments. The invention further relates to materials such as retroreflective sheetings, pavement markings and beaded projection screens comprising a binder and the surface treated optical elements. The fluorochemical surface treatment comprises at least two linkages selected from urethane linkages, ester linkages or phosphate linkages; and at least one perfluorinated group.
Beaded projection display screens, retroreflective sheeting used in the manufacture of roadway signs, and retroreflective paints typically include optical elements adhered through the use of a binder. In the case of beaded projection display materials, the optical elements are microscopic glass beads that act as lenses to collect projected light from the rear of the screen and focus it to relatively small spots, near the surfaces of the microspheres. The foci are approximately in the areas where the optical elements contact a front support layer. In other retroreflective materials, the optical elements act as lenses which focus the light onto a reflector (metal mirror of diffusely reflecting pigment) and once the light has been reflected off the reflector the microspheres again act as lenses to resend the light back toward the incoming light source. In order to contribute the desired retroreflective property, however, it is important that a layer of glass microspheres be present on the surface of the binder layer.
As discussed in U.S. Pat. No. 3,222,204, ordinary glass beads tend to sink into the uncured liquid binder layer. In instances wherein the individual beads are not entirely submerged, the optical properties of the bead can also be impaired by the binder wetting out the bead surface and spreading on the exposed bead surface. To address this problem, U.S. Pat. No. 3,222,204 teaches coating the glass beads with a thin surface coating of an oleophobic fluorocarbon-sizing agent. At column 5, lines 61-75, this reference states that, xe2x80x9cAqueous treating solutions of fluorocarbon chromium coordination complexes are preferred and are described in U.S. Pat. No. 2,662,835 (Dec. 15, 1953) and U.S. Pat. No. 2,809,990 (Oct. 15, 1957) and U.S. Pat. No. 2,934,450 (Apr. 26, 1960). The complex may be made by reacting chromyl chloride with a fluorocarbon monocarboxylic acid (having a highly fluorinated terminal chain or tail containing 4 to 10 carbon atoms) in an isopropanol vehicle that serves as both a solvent and reducing agent, the chromium to acid mole ratio being in the range of 2:1 to 5:1. The resultant green-colored isopropanol solution of the complex is diluted with water at the time of use. The fluorocarbon acid preferably has 6 to 8 fully fluorinated (perfluorinated) carbon atoms in the terminal fluorocarbon chain or tail.xe2x80x9d Specific working examples include chromium coordination complexes of perfluorooctanoic acid and N-ethyl-N-perfluorooctanesulfonyl glycine.
U.S. Pat. No. 4,713,295 teaches coating glass beads with a mixture of substances. The mixture comprises a first substance which if used alone would tend to make the beads hydrophobic while leaving them oleophilic and a second substance which if used alone would tend to make the beads both hydrophobic and oleophobic. xe2x80x9cFor the best results, it is preferred to use a second substance which is an anionic fluorocarbon compound, and optimally, said second substance is a fluoro-alkyl-sulphonate, for example a fluoro-alkyl-sulphonate in which the alkyl has a long chain (C14 to C18).xe2x80x9d (See Column 4, lines 8-13). The exemplified hydrophobic and oleophobic substance is a potassium fluoroalkyl-sulphonate (for example FC129 from 3M). (See column 5, lines 50-52) FC129 is a potassium fluoroctyl sulphonyl-containing compound.
The present invention relates to fluorochemicals suitable for use as a surface treatment to induce float of optical elements. The fluorochemicals comprise the reaction product of at least one hydroxyl group containing material and a coreactant including polyisocyanates, polycarboxylic acids and derivatives thereof, or (poly)phosphoric acid derivatives. At least one reactant or coreactant comprises a fluorinated group. Preferably, at least one reactant or coreactant comprises a water-solubilizing group or silane group. Preferred fluorinated groups include perfluoroalkyl and perfluoroheteroalkyl, preferably having 2 to 6 and more preferably no more than 4 carbon atoms. The hydroxyl group containing material may be a fluorinated monoalcohol, fluorinated polyol or mixture thereof. Alternatively a non-fluorinated polyol may be employed as the hydroxyl containing material, preferably in combination with a fluorinated monoalcohol. The hydroxyl group containing material and/or the coreactant may be substituted with a water-solubilizing group and/or a silane group. Further, the reaction product may further comprise a long chain hydrocarbon monoalcohol, a monofunctional fluorochemical, a water-solubilizing group containing ingredient, a silane group containing ingredient or mixture thereof.
The invention further relates to optical elements comprising a fluorochemical surface treatment wherein the fluorochemical comprises at least two linkages selected from urethane linkages, ester linkages or phosphate linkages; and at least one perfluorinated group with the provision that wherein the linkages are urethane the fluorochemical surface treatment is free of oxygen in the backbone.
In another embodiment, the invention relates to a method of coating optical elements comprising the steps of providing a surface treatment composition comprising a solvent and the previously described fluorochemical surface treatment, coating optical elements with the composition; and drying the composition. The solvent is preferably water, optionally comprising from 0 to about 30 wt-% of a cosolvent.
In other embodiments, the invention relates to a pavement marking, a reflective sheeting, and a rear projection screen comprising a binder and a multitude of the surface treated optical elements. The optical elements are embedded in the binder at a depth of about 40-70% of their diameters.
The present invention relates to optical elements such as glass beads coated with a fluorochemical surface treatment. The terminology xe2x80x9coptical elementxe2x80x9d refers to a material having a particle size ranging from about 25 to 1000 microns and having a refractive index ranging from about 1.5 to about 2.3 and higher.
The optical elements have at least one dimension that is no larger than 2 millimeters and preferably no larger than 250 microns. The optical elements may be in the form of any shape such as granules, flakes and fibers. However, spheroidal glass elements, denoted as xe2x80x9cglass beadsxe2x80x9d, xe2x80x9cbeadsxe2x80x9d and xe2x80x9cmicrospheresxe2x80x9d hereinafter are preferred for materials such as retroreflective articles (e.g. retroreflective sheetings, pavement markings and beaded projection screens).
During the manufacture of retroreflective materials, optical elements are fixed in place by means of a liquid binder. Optical elements have a density or specific gravity several times that of the liquid binder, causing the optical elements to sink into the liquid binder layer, rather than float on the surface.
Preferred properties of optical elements will be described herein with respect to glass beads. Ordinary glass beads typically have a density of about 2.5 and a refractive index of about 1.5. xe2x80x9cHigh indexxe2x80x9d beads refers to beads having a density of about 3.5 and a refractive index of about 1.9, whereas xe2x80x9csuper high indexxe2x80x9d typically refers to beads having a density of about 5 and a refractive index of about 2.3 or higher. The diameter of the glass beads typically ranges from a few microns to approximately 2500 microns and is preferably from about 25 to 1000 microns.
In addition to having the desired particle size and refractive index, the glass beads are typically transparent. The term transparent means that when viewed under an optical microscope (e.g., at 100xc3x97) the microspheres have the property of transmitting rays of visible light so that bodies beneath the microspheres, such as bodies of the same nature as the microspheres can be clearly seen through the microspheres, when both are immersed in oil of approximately the same refractive index as the microspheres. The outline, periphery or edges of bodies beneath the microspheres are clearly discernible. Although the oil should have a refractive index approximating that of the microspheres, it should not be so close that the microspheres seem to disappear as would be the case for a perfect match.
The optical elements may comprise microspheres that are ceramic. In general, ceramic microsphere optical elements are comprised of metal oxides that are substantially colorless. Suitable metal oxides include Al2O3, SiO2, ThO2, SnO2, TiO2, Y2O3 and ZrO2 with the oxides of zirconium, silicon, and titanium being preferred. The ceramic microspheres can exhibit a range of properties, depending on the kind and amounts of the various metal oxides employed as well as the method of manufacture. Preferred, however, are dense microspheres having substantially no open porosity that have an average hardness greater than sand.
Additional information concerning the desired properties for various end-uses and methods of manufacture of microspheres (e.g. sol-gel process), can be found in U.S. Pat. Nos. 3,493,403; 3,709,706; and 4,564,556; incorporated herein by reference. Glass beads suitable for use as optical elements in the invention are also commercially available from Flex-O-Lite Corporation, Fenton, Mo. and Nippon Electric Glass, Osaka, Japan.
The optical elements of the invention are coated with a surface treatment that alters the floatation properties of the optical element in the liquid binder. xe2x80x9cFloatxe2x80x9d and derivations thereof, described in the context of glass beads, refers to the beads assuming a position wherein slightly more than half of each bead is submerged. The liquid binder preferably contacts the embedded beads only up to 5 to 30xc2x0 above their equators. The floatability of the glass beads can be affected to some extent by the particle size, particle size distribution, surface chemistry and chemical make-up of the particular glass beads as well as the chemical make-up, density, and viscosity of the binder. In general, however, only about 10% or less of the glass beads tend to float in heptane test liquid in the absence of an effective surface treatment.
The position that the glass beads attain relative to the undisturbed binder due to the surface treatment assists the anchoring of the beads in the ultimate dried or solidified binder coating. The glass beads are preferably embedded to about 40-70%, and more preferably to about 40-60% of their diameters. The beads are adequately exposed providing a sphere-lens having a large optical aperture relative to its size. During the drying or solidification of the binder, there is some shrinkage of the binder film. However, the beads remain bonded with the centers of the floated beads being approximately equidistant from the underlying back surface of the binder layer or the top surface of the base.
In addition to the improvement in floatation of the optical elements, it is also important that the surface treatment does not adversely affect the adhesion of the optical elements with the liquid binder. The adhesion can be evaluated in several ways and will be described herein with respect to a preferred optical element, glass beads. The initial adhesion can subjectively determined by estimating the depth to which the embedded glass beads have sunk into the binder after curing. The glass beads are preferably embedded to a depth of about 40-70%, and more preferably to about 40-60% of their diameters. Another way of evaluating adhesion is accelerated aging evaluations. A piece of cured glass bead-embedded binder is conditioned in boiling water for 24 hours. After conditioning, the glass beads are preferably embedded to the same extent as prior to conditioning and the individual glass beads are difficult to remove with a dissection probe. Yet another way to evaluate the effect of the binder on adhesion is comparative tensile testing. A uniform slurry of binder and untreated glass beads at a ratio of about 1 to 3 is drawn down into a film having a thickness of about 0.4 mm. A second slurry of binder and surface treated glass beads employing the same ratio of ingredients and film thickness is prepared. After the samples are fully cured, the samples are conditioned for 24 hours in water at ambient temperature. Tensile testing is conducted with a 1xe2x80x3 (2.5 cm) wide sample employing a 2xe2x80x3 (5 cm) gap at a rate of 0.5 inches (1.3 cm)/minute. The stress at break of the sample comprising the surface treated beads is about the same as or preferably greater than the control sample, comprising untreated beads (xe2x89xa7about 90% of the standard deviation of the average value). Any one of the previously described methods is typically sufficient to determine whether the surface treatment adversely affects the adhesion of the glass beads with the liquid binder. Preferably, however, all three of the evaluations are conducted.
The optical elements are coated with a fluorochemical surface treatment. As used herein xe2x80x9csurface treatmentxe2x80x9d refers to a composition that causes at least about 90% of the optical elements to float in heptane or an aromatic solvent, such as toluene.
The following definition of terms is used in the specification and claims with regard to the description of the fluorochemical surface treatments, unless otherwise stated:
xe2x80x9cAcyloxyxe2x80x9d means a radicalxe2x80x94OC(O)R where R is, alkyl, alkenyl, and cycloalkyl, e.g., acetoxy, 3,3,3-trifluoroacetoxy, propionyloxy, and the like.
xe2x80x9cAlkoxyxe2x80x9d means a radicalxe2x80x94OR where R is an alkyl group as defined below, e.g., methoxy, ethoxy, propoxy, butoxy, and the like.
xe2x80x9cAlkylxe2x80x9d means a linear saturated monovalent hydrocarbon radical having from one to about twelve carbon atoms or a branched saturated monovalent hydrocarbon radical having from three to about twelve carbon atoms, e.g., methyl, ethyl, 1-propyl, 2-propyl, pentyl, and the like.
xe2x80x9cAlkylenexe2x80x9d means a linear saturated divalent hydrocarbon radical having from one to about twelve carbon atoms or a branched saturated divalent hydrocarbon radical having from three to about twelve carbon atoms, e.g., methylene, ethylene, propylene, 2-methylpropylene, pentylene, hexylene, and the like.
xe2x80x9cAralkylenexe2x80x9d means an alkylene radical defined above with an aromatic group attached to the alkylene radical, e.g., benzyl, pyridylmethyl, 1-naphthylethyl, and the like. xe2x80x9cFluorocarbon monoalcoholxe2x80x9d and xe2x80x9cfluorinated monalcoholxe2x80x9d mean a compound having one hydroxyl group and a perfluoroalkyl or a perfluoroheteralkyl group, e.g. C4F9SO2N(CH3)CH2CH2OH, C4F9CH2CH2OH, C2F5O(C2F4O3CF2CONHC2H4OH, cxe2x80x94C6F11CH2OH, and the like.
xe2x80x9cHeteroacyloxyxe2x80x9d has essentially the meaning given above for acyloxy except that one or more heteroatoms (i.e. oxygen, sulfur, and/or nitrogen) may be present in the R group and the total number of carbon atoms present may be up to 50, e.g., CH3CH2OCH2CH2C(O)Oxe2x80x94, C4H9OCH2CH2OCH2CH2C(O)Oxe2x80x94, CH3O(CH2CH2O)nCH2CH2C(O)Oxe2x80x94, and the like.
xe2x80x9cHeteroalkoxyxe2x80x9d has essentially the meaning given above for alkoxy except that one or more heteroatoms (i.e. oxygen, sulfur, and/or nitrogen) may be present in the alkyl chain and the total number of carbon atoms present may be up to 50, e.g. CH3CH2OCH2CH2Oxe2x80x94, C4H9OCH2CH2OCH2CH2Oxe2x80x94, CH3O(CH2CH2O)nH, and the like.
xe2x80x9cHeteroalkylxe2x80x9d has essentially the meaning given above for alkyl except that one or more heteroatoms (i.e. oxygen, sulfur, and/or nitrogen) may be present in the alkyl chain, these heteroatoms being separated from each other by at least one carbon, e.g., CH3CH2OCH2CH2xe2x80x94, CH3CH2OCH2CH2OCH(CH3)CH2xe2x80x94, C4F9CH2CH2SCH2CH2xe2x80x94, and the like.
xe2x80x9cHeteroaralkylenexe2x80x9d means an aralkylene radical defined above except that catenated oxygen, sulfur, and/or nitrogen atoms may be present, e.g., phenyleneoxymethyl, phenyleneoxyethyl, benzyleneoxymethyl, and the like.
xe2x80x9cHaloxe2x80x9d means fluoro, chloro, bromo, or iodo, preferably fluoro and chloro.
xe2x80x9cLong-chain hydrocarbon monoalcoholxe2x80x9d means a compound having one hydroxyl group and a long chain hydrocarbon group having 10 to 18 carbons which may be saturated, unsaturated, or aromatic, and may optionally be substituted with one or more chlorine, bromine, trifluoromethyl, or phenyl groups, e.g. CH3(CH2)10CH2OH, CH3(CH2)14CH2OH, and the like.
xe2x80x9cOligomerxe2x80x9d means a polymer molecule consisting of only a few (for example, from 2 to about 20) repeat (polymerized) units.
xe2x80x9cPerfluoroalkylxe2x80x9d has essentially the meaning given above for xe2x80x9calkylxe2x80x9d except that all or essentially all of the hydrogen atoms of the alkyl radical are replaced by fluorine atoms and the number of carbon atoms is from 3 to about 8, e.g. perfluoropropyl, perfluorobutyl, perfluorooctyl, and the like.
xe2x80x9cPerfluoroalkylenexe2x80x9d has essentially the meaning given above for xe2x80x9calkylenexe2x80x9d except that all or essentially all of the hydrogen atoms of the alkylene radical are replaced by fluorine atoms, e.g., perfluoropropylene, perfluorobutylene, perfluorooctylene, and the like
xe2x80x9cPerfluoroheteroalkylxe2x80x9d has essentially the meaning given above for xe2x80x9cheteroalkylxe2x80x9d except that all or essentially all of the hydrogen atoms of the heteroalkyl radical are replaced by fluorine atoms and the number of carbon atoms is from 3 to about 100, e.g. CF3CF2OCF2CF2xe2x80x94, CF3CF2O(CF2CF2O)3CF2CF2xe2x80x94, C3F7O(CF(CF3)CF2O)mCF(CF3)CF2xe2x80x94 where m is from about 10 to about 30, and the like.
xe2x80x9cPerfluorinated groupxe2x80x9d means an organic group wherein all or essentially all of the carbon bonded hydrogen atoms are replaced with fluorine atoms, e.g. perfluoroalkyl, perfluoroheteroalkyl, and the like.
xe2x80x9cPolyfunctional isocyanate compoundxe2x80x9d means a compound containing two or more isocyanate radicals, xe2x80x94NCO, attached to a multivalent organic group, e.g. hexamethylene diisocyanate, the biuret and iscyanurate of hexamethylene diisocyanate, and the like.
xe2x80x9cPolyolxe2x80x9d means an organic compound or polymer with an average of at least about 2 primary or secondary hydroxyl groups per molecule, e.g. ethylene glycol, propylene glycol, 1,6-hexanediol, and the like.
xe2x80x9cSilane groupxe2x80x9d means a group comprising silicon to which at least one hydrolyzable group is bonded, e.g. xe2x80x94Si(OCH3)3, xe2x80x94Si(OOCCH3)2CH3, xe2x80x94Si(Cl)3, and the like.
The surface treatment generally comprises at least one fluorochemical, wherein the fluorochemical comprises at least two linkages selected from urethane linkages or ester linkages or phosphate linkages. The fluorochemical comprises at least one pendant and/or terminal fluorinated (e.g. perfluorinated) group. For embodiments wherein the linkages are urethane linkages, the fluorochemical is free of oxygen in the backbone. Such surface treatments generally comprise the reaction product of at least one hydroxyl group containing material with at least one coreactant selected from polyfunctional isocyanate(s) or polycarboxylic acid(s) and derivatives thereof or (poly)phosphoric acid derivatives; and optionally at least one second coreactant The terminology xe2x80x9c(poly)phosphoric acid derivativexe2x80x9d refers to derivatives of phosphoric acid (e.g. salt) as well as derivatives having one or more of such groups (e.g. polyphosphates). At least one reactant or coreactant is fluorinated. The surface treatment generally comprises at least one water-solubilizing group or at least one silane groups. Such groups may independently be pendant from the repeating unit or terminal. Such groups aid in forming aqueous solutions, dispersions or emulsion from such fluorochemicals. Further, such groups improve the adhesion of the surface treatment to the optical element (e.g. glass or glass/ceramic beads) surface. In some embodiment the water-solubilizing group is present in view of the selection of coreactant. (e.g. (poly)phosphoric acid derivative). In other embodiments the water-solubilizing group is present by employing a hydroxyl containing material and/or coreactant that has been substituted with one or more of such water-solubilizing groups. Alternatively or in addition thereto, a second coreactant may be employed that comprises such water-solubilizing group(s).
The general structure of preferredsurface treatments may be represented by the following formula:
R1Oxe2x80x94[Xxe2x80x94Q(A)mxe2x80x94Xxe2x80x94OR2Oxe2x80x94]nxe2x80x94Xxe2x80x94Q(A)mxe2x80x94Xxe2x80x94OR1xe2x80x83xe2x80x83(Formula I)
R1 is selected from RfZR3, H, (Y)3SiR3, MOC(O)R3, long chain alkyl group or combination thereof wherein;
RfZR3xe2x80x94 is a residue of at least one of the fluorochemical monoalcohols;
Rf is a perfluoroalkyl group having 3 to about 12 carbon atoms, or a perfluoroheteroalkyl group having 3 to about 50 carbon atoms;
Z is a covalent bond, sulfonamido (xe2x80x94SO2NR4xe2x80x94), or carboxamido (xe2x80x94CONR4xe2x80x94) linkage, where R4 is hydrogen or alkyl;
R3 is a divalent straight or branched chain alkylene, cycloalkylene, or heteroalkylene group of 1 to 14 carbon atoms;
M is Rxe2x80x2O, H, NH4, Na, K, Rxe2x80x2O or combination;
each Y is independently a hydroxy; a hydrolyzable moiety selected from the group consisting of alkoxy, acyloxy, heteroalkoxy, heteroacyloxy, halo, and oxime; or a non-hydrolyzable moiety selected from the group consisting of phenyl, alicyclic, straight-chain aliphatic, and branched-chain aliphatic, wherein at least one Y is a hydrolyzable moiety.
X is xe2x80x94C(O)NHxe2x80x94, xe2x80x94C(O)xe2x80x94, or P(O)(OM)xe2x80x94
Q is a multi-valent organic group which is a residue of the polyfunctional isocyanate, carboxyl or phosphonyl compound;
R2 is a divalent organic group which is a residue of the polyol and may be substituted with or contain (i) water-solubilizing groups selected from the group consisting of carboxylate, sulfate, sulfonate, phosphonate, polyethylene oxide, ammonium, quaternary ammonium, and mixtures thereof and (ii) perfluorinated groups;
A is Rxe2x80x2xe2x80x94O or R1xe2x80x94Oxe2x80x94X;
m is an integer from 0 to 2; and
n is an integer from 0 to 20.
Preferred surface treatments are substantially free of perfluoroalkyl side chains and end groups having more than 6, and more preferably substantially free of perfluoroalkyl side chains and end groups having more than 4 carbon atoms. xe2x80x9cSubstantially freexe2x80x9d refers to the presence of less than about 1 wt-% of such fluoroalkyl segments as can be detected by means of x-ray photoelectron spectroscopy (XPS) or time of flight secondary ion mass spectrometry.
The hydroxyl group containing material typically comprises a fluorinated polyol, a fluorinated monoalcohol, or mixture thereof. Alternatively, however, a non-fluorinated monoalcohol or non-fluorinated polyol may be employed as the hydroxyl group containing material with the proviso that a fluorinated coreactant is provided.
Organic polyols for use in the invention have an average hydroxyl functionality of at least about 2 (preferably, about 2 to 5; more preferably, about 2 to 3; most preferably, about 2, as diols are most preferred). The hydroxyl groups can be primary or secondary, with primary hydroxyl groups being preferred for their greater reactivity. Mixtures of diols with polyols that have an average hydroxyl functionality of about 2.5 to 5 (preferably about 3 to 4; more preferably, about 3) can also be used. Such mixtures may contain no more than about 20 percent by weight of such polyols, no more than about 10 percent, and no more than about 5 percent.
Suitable polyols include those that comprise at least one aliphatic, heteroaliphatic, alicyclic, heteroalicyclic, aromatic, heteroaromatic, or polymeric moiety. Preferred polyols are aliphatic or polymeric polyols that contain hydroxyl groups as terminal groups or as groups that are pendant from the backbone chain of the polyol.
The molecular weight (that is, the number average molecular weight) of hydrocarbon polyols can generally vary from about 60 to about 2000, preferably, from about 60 to about 1000, more preferably, from about 60 to about 500, most preferably, from about 60 to about 300. The equivalent weight (that is, the number average equivalent weight) of hydrocarbon polyols generally can be in the range of about 30 to about 1000, preferably, from about 30 to about 500, more preferably, from about 30 to about 250. If the polyol comprises a perfluoropolyether, it can have a molecular weight as high as approximately 7000.
The polyols or fluorinated alcohols can be substituted with or contain other groups. Thus, the hydroxyl group containing material may be a branched or straight chain hydrocarbon, an alcohol or polyol containing at least one solubilizing group, a fluorinated alcohol or polyol comprising a monovalent or divalent perfluorinated group, an alcohol or polyol comprising a silane group, a polyalkylsiloxane alcohol or polyol (e.g. xe2x80x94(Si(Ar)2O)xe2x80x94, e.g. HOR[Si(C6H5)2O]SiROH, wherein each R is independently straight or branched chain alkyl; xe2x80x94(Si(R)2O)xe2x80x94, e.g. HOR[Si(CH3)2O]nSiROH, wherein each R is independently straight or branched chain alkyl. Solubilizing groups include carboxylate, sulfate, sulfonate, phosphate, phosphonate, ammonium, quaternary ammonium, and the like.
The perfluorinated groups may be perfluoroalkyl and perfluoroheteroalkyl. Perfluoroalkyl groups are preferred, with perfluoroalkyl groups having from 2 to 6 carbon atoms being more preferred and perfluoroalkyl groups having 4 carbon atoms being most preferred.
The silane groups of the hydroxyl group containing material may contain one, two, or three hydrolyzable groups on the silicon atom. Polyalkylsiloxane hydroxyl group containing materials include, but are not limited to, hydroxyalkyl terminated polydimethyl siloxanes, polymethyloctadecylsiloxane, polydimethylmethyloctadecylsiloxane, polydimethyldodecyltetradecylsiloxane, polymethylhexadecylsiloxane, polymethyloctylsiloxane, polymethyl-3,3,3-trifluoropropylsiloxane, and the like. Polyarylsiloxane diols are essentially the same as the polyalkylsiloxanes with some or all of the methyl groups replaced with phenyl groups, such as hydroxyalkyl terminated polydiphenylsiloxane and hydroxyalkyl terminated dimethyl-diphenylsiloxane copolymer.
Representative examples of suitable non-polymeric polyols that may be employed in combination with a fluorinated ingredient (e.g. fluorinated polyol, fluorinated alchohol) include alkylene glycols, polyhydroxyalkanes, and other polyhydroxy compounds. The alkylene glycols include, for example, 1,2-ethanediol; 1,2-propanediol; 3-chloro-1,2-propanediol; 1,3-propanediol; 1,3-butanediol; 1,4-butanediol; 2-methyl-1,3-propanediol; 2,2-dimethyl-1,3-propanediol (neopentylglycol); 2-ethyl-1,3-propanediol; 2,2-diethyl-1,3-propanediol; 1,5-pentanediol; 2-ethyl-1,3-pentanediol; 2,2,4-trimethyl-1,3-pentanediol; 3-methyl-1,5-pentanediol; 1,2-, 1,5-, and 1,6-hexanediol; 2-ethyl-1,6-hexanediol; bis(hydroxymethyl)cyclohexane; 1,8-octanediol; bicyclo-octanediol; 1,10-decanediol; tricyclo-decanediol; norbornanediol; and 1,18-dihydroxyoctadecane.
The polyhydroxyalkanes include, for example, glycerine; trimethylolethane; trimethylolpropane; 2-ethyl-2-(hydroxymethyl)-1,3-propanediol; 1,2,6-hexanetriol; pentaerythritol; quinitol; mannitol; and sorbitol.
Other polyhydroxy compounds include, for example, such as 2,2-bis(hydroxymethyl)propionic acid; di(ethylene glycol); tri(ethylene glycol); tetra(ethylene glycol); tetramethylene glycol; dipropylene glycol; diisopropylene glycol; tripropylene glycol; bis(hydroxymethyl)propionic acid; N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane; bicine; N-bis(2-hydroxyethyl)perfluorobutylsulfonamide; 1,11-(3,6-dioxaundecane)diol; 1,14-(3,6,9,12-tetraoxatetradecane)diol; 1,8-(3,6-dioxa-2,5,8-trimethyloctane)diol; 1,14-(5,10-dioxatetradecane)diol; castor oil; 2-butyne-1,4-diol; N,N-bis(hydroxyethyl)benzamide; 4,4xe2x80x2-bis(hydroxymethyl)diphenylsulfone; 1,4-benzenedimethanol; 1,3-bis(2-hydroxyethyoxy)benzene; 1,2-dihydroxybenzene; resorcinol; 1,4-dihydroxybenzene; 3,5-, 2,6-, 2,5-, and 2,4-dihydroxybenzoic acid; 1,6-, 2,6-, 2,5-, and 2,7-dihydroxynaphthalene; 2,2xe2x80x2- and 4,4xe2x80x2-biphenol; 1,8-dihydroxybiphenyl; 2,4-dihydroxy-6-methyl-pyrimidine; 4,6-dihydroxypyrimidine; 3,6-dihydroxypyridazine; bisphenol A; 4,4xe2x80x2-ethylidenebisphenol; 4,4xe2x80x2-isopropylidenebis(2,6-dimethylphenol); bis(4-hydroxyphenyl)methane; 1,1-bis(4-hydroxyphenyl)-1-phenylethane (bisphenol C); 1,4-bis(2-hydroxyethyl)piperazine; bis(4-hydroxyphenyl) ether; as well as other aliphatic, heteroaliphatic, saturated alicyclic, aromatic, saturated heteroalicyclic, and heteroaromatic polyols; and the like, and mixtures thereof.
Representative examples of useful polymeric polyols include polyoxyethylene, polyoxypropylene, and ethylene oxide-terminated polypropylene glycols and triols of molecular weights from about 200 to about 2000, corresponding to equivalent weights of about 100 to about 1000 for the diols or about 70 to about 700 for triols; polytetramethylene glycols of varying molecular weight; polydialkylsiloxane diols of varying molecular weight; hydroxy-terminated polyesters and hydroxy-terminated polylactones (e.g., polycaprolactone polyols); hydroxy-terminated polyalkadienes (e.g., hydroxy-terminated polybutadienes); and the like. Mixtures of polymeric polyols can be used if desired.
Useful commercially available polymeric polyols include Carbowax(trademark) poly(ethylene glycol) materials in the number average molecular weight (Mn) range of from about 200 to about 2000 (available from Union Carbide Corp.); poly(propylene glycol) materials such as PPG-425 (available from Lyondell Chemicals); block copolymers of poly(ethylene glycol) and poly(propylene glycol) such as Pluronic(trademark) L31 (available from BASF Corporation); fluorinated oxetane polyols made by the ring-opening polymerization of fluorinated oxetane such as Poly-3-Fox(trademark) (available from Omnova Solutions, Inc., Akron Ohio); polyetheralcohols prepared by ring opening addition polymerization of a fluorinated organic group substituted epoxide with a compound containing at least two hydroxyl groups as described in U.S. Pat. No. 4,508,916 (Newell et al); Bisphenol A ethoxylate, Bisphenol A propyloxylate, and Bisphenol A propoxylate/ethoxylate (available from Sigma-Aldrich); polytetramethylene ether glycols such as Polymeg(trademark) 650 and 1000 (available from Quaker Oats Company) and the Terathane(trademark) polyols (available from DuPont); hydroxy-terminated polybutadiene resins such as the Poly bd(trademark) materials (available from Elf Atochem); the xe2x80x9cPePxe2x80x9d series (available from Wyandotte Chemicals Corporation) of polyoxyalkylene tetrols having secondary hydroxyl groups, for example, xe2x80x9cPePxe2x80x9d 450, 550, and 650; polycaprolactone polyols with M, in the range of about 200 to about 2000 such as Tone(trademark) 0201, 0210, 0301, and 0310 (available from Union Carbide); xe2x80x9cParaplex(trademark) U-148xe2x80x9d (available from Rohm and Haas), an aliphatic polyester diol; polyester polyols such as the Multron(trademark) poly(ethyleneadipate)polyols (available from Mobay Chemical Co.); polycarbonate diols such as Duracarb(trademark) 120, a hexanediol carbonate with Mn=900 (available from PPG Industries Inc.); and the like; and mixtures thereof.
Alternatively or in addition thereto, the hydroxyl group containing material may comprise a fluorinated monoalcohol. The fluorinated monoalcohol can contain straight chain, branched chain, or cyclic fluorinated alkylene groups or any combination thereof. The fluorinated monoalcohol can optionally contain one or more heteroatoms (i.e. oxygen, sulfur, and/or nitrogen) in the carbon-carbon chain so as to form a carbon-heteroatom-carbon chain (i.e. a heteroalkylene group). Fully-fluorinated groups are generally preferred, but hydrogen or chlorine atoms can also be present as substituents, provided that no more than one atom of either is present for every two carbon atoms. The terminal portion of the group is generally fully-fluorinated, preferably containing at least three fluorine atoms, e.g., CF3Oxe2x80x94, CF3CF2xe2x80x94, CF3CF2CF2xe2x80x94, (CF3)2Nxe2x80x94, (CF3)2CFxe2x80x94, SF5CF2xe2x80x94. Perfluorinated aliphatic groups (i.e., those of the formula CnF2n+1xe2x80x94) wherein n is 2 to 6 inclusive are the preferred Rf groups, with n=3 to 5 being more preferred and with n=4 being the most preferred. Preferred fluorine-containing monoalcohols include alcohol terminated hexafluoropropylene oxide derivatives. If desired, similar thiols rather than alcohols, can be utilized as well.
Polyfunctional isocyanate compounds useful in the preparation of the fluorinated polyurethane surface treatments comprise isocyanate radicals attached to the multivalent organic group, Q, which can comprise a multivalent aliphatic, alicyclic, or aromatic moiety; or a multivalent aliphatic, alicyclic or aromatic moiety attached to a biuret, an isocyanurate, or a uretdione, or mixtures thereof. Preferred polyfunctional isocyanate compounds contain two or three xe2x80x94NCO radicals. Compounds containing two xe2x80x94NCO radicals are comprised of divalent aliphatic, alicyclic, araliphatic, or aromatic moieties to which the xe2x80x94NCO radicals are attached. Preferred compounds containing three xe2x80x94NCO radicals are comprised of isocyanatoaliphatic, isocyanatoalicyclic, or isocyanatoaromatic, monovalent moieties, which are attached to a biuret or an isocyanurate. Such isocyanates may be fluorinated.
Representative examples of suitable polyfunctional isocyanate compounds include isocyanate functional derivatives of the polyfunctional isocyanate compounds as defined herein. Examples of derivatives include, but are not limited to, those selected from the group consisting of ureas, biurets, allophanates, dimers and trimers (such as uretdiones and isocyanurates) of isocyanate compounds, and mixtures thereof. Any suitable organic polyisocyanate, such as an aliphatic, alicyclic, araliphatic, or aromatic polyisocyanate, may be used either singly or in mixtures of two or more. The aliphatic polyfunctional isocyanate compounds generally provide better light stability than the aromatic compounds. Aromatic polyfunctional isocyanate compounds, on the other hand, are generally more economical and reactive toward polyols and other poly(active hydrogen) compounds than are aliphatic polyfunctional isocyanate compounds. Suitable aromatic polyfunctional isocyanate compounds include, but are not limited to, those selected from the group consisting of 2,4-toluene diisocyanate (TDI), 2,6-toluene diisocyanate, an adduct of TDI with trimethylolpropane (available as Desmodur(trademark) CB from Bayer Corporation, Pittsburgh, Pa.), the isocyanurate trimer of TDI (available as Desmodur(trademark) IL from Bayer Corporation, Pittsburgh, Pa.), diphenylmethane 4,4xe2x80x2-diisocyanate (MDI), diphenylmethane 2,4xe2x80x2-diisocyanate, 1,5-diisocyanato-naphthalene, 1,4-phenylene diisocyanate, 1,3-phenylene diisocyanate, 1-methyoxy-2,4-phenylene diisocyanate, 1-chlorophenyl-2,4-diisocyanate, and mixtures thereof.
Examples of useful alicyclic polyfunctional isocyanate compounds include, but are not limited to, those selected from the group consisting of dicyclohexylmethane diisocyanate (H12MDI, commercially available as Desmodur(trademark) W, available from Bayer Corporation, Pittsburgh, Pa.), 4,4xe2x80x2-isopropyl-bis(cyclohexylisocyanate), isophorone diisocyanate (IPDI), cyclobutane-1,3-diisocyanate, cyclohexane 1,3-diisocyanate, cyclohexane 1,4-diisocyanate (CHDI), 1,4-cyclohexanebis(methylene isocyanate) (BDI), 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, and mixtures thereof.
Examples of useful aliphatic polyfunctional isocyanate compounds include, but are not limited to, those selected from the group consisting of 1,4-tetramethylene diisocyanate, hexamethylene 1,4-diisocyanate, hexamethylene 1,6-diisocyanate (HDI), 1,12-dodecane diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate (TMDI), 2,4,4-trimethyl-hexamethylene diisocyanate (TMDI), 2-methyl-1,5-pentamethylene diisocyanate, dimer diisocyanate, the urea of hexamethylene diisocyanate, the biuret of hexamethylene 1,6-diisocyanate (HDI) (available as Desmodur(trademark) N-100 and N-3200 from Bayer Corporation, Pittsburgh, Pa.), the isocyanurate of HDI (available as Demodur(trademark) N-3300 and Desmodur(trademark) N-3600 from Bayer Corporation, Pittsburgh, Pa.), a blend of the isocyanurate of HDI and the uretdione of HDI (available as Desmodur(trademark) N-3400 available from Bayer Corporation, Pittsburgh, Pa.), and mixtures thereof.
Examples of useful araliphatic polyisocyanates include, but are not limited to, those selected from the group consisting of m-tetramethyl xylylene diisocyanate (m-TMXDI), p-tetramethyl xylylene diisocyanate (p-TMXDI), 1,4-xylylene diisocyanate (XDI), 1,3-xylylene diisocyanate, p-(1-isocyanatoethyl)-phenyl isocyanate, m-(3-isocyanatobutyl)-phenyl isocyanate, 4-(2-isocyanatocyclohexyl-methyl)-phenyl isocyanate, and mixtures thereof.
Suitable commercially available polyfunctional isocyanates are exemplified by Desmodur(trademark) N-3200, Desmodur(trademark) N-3300, Desmodur(trademark) N-3400, Desmodur(trademark) N-3600, Desmodur(trademark) H (HDI), Desmodur(trademark) W (bis[4-isocyanatocyclohexyl]methane), Mondur(trademark) M (4,4xe2x80x2-diisocyanatodiphenylmethane), Mondur(trademark) TDS (98% toluene 2,4-diisocyanate), Mondur(trademark) TD-80 (a mixture of 80% 2,4 and 20% 2,6-toluene diisocyanate isomers), and Desmodur(trademark) N-100, each available from Bayer Corporation, Pittsburgh, Pa.
Other useful triisocyanates are those obtained by reacting three moles of a diisocyanate with one mole of a triol. For example, toluene diisocyanate, 3-isocyanatomethyl-3,4,4-trimethylcyclohexyl isocyanate, or m-tetramethylxylene diisocyanate can be reacted with 1,1,1-tris(hydroxymethyl)propane to form triisocyanates. The product from the reaction with m-tetramethylxylene diisocyanate is commercially available as CYTHANE 3160 (American Cyanamid, Stamford, Conn.).
In the preparation of the fluorinated (poly)esters the hydroxyl group containing material is reacted with at least one polycarboxylic acid or derivative thereof, such as dicarboxylic acid halides, dicarboxylic acid anhydrides, and dicarboxylic acid esters. Suitable polycarboxylic acids and derivatives thereof for use in preparing the fluorochemical composition comprise at least one aliphatic, heteroaliphatic (that is, containing in-chain heteroatoms, such as nitrogen, oxygen, or sulfur), saturated alicyclic, saturated heteroalicyclic, or polymeric moiety. The compounds can optionally contain one or more xe2x80x9cnon-interferingxe2x80x9d groups (groups that do not interfere with the reactivity of the acyl groups, do not cause undesirable side reactions, and do not cause decomposition of the resulting fluorochemical composition), for example, alkyl, sulfonate, ester, ether, halo, haloalkyl, amide, or carbamate groups. Preferably, the compounds are aliphatic in nature.
Derivatives are sometimes preferred over acids for a variety of reasons. For example, halides provide both relatively fast reaction rates and reactions that tend to go to completion. The resulting HCl is volatile and can be removed under vacuum or by other removal means, such as by water washing.
Anhydrides can also be used. Particularly useful anhydride derivatives of dicarboxylic acids are cyclic anhydrides, which react relatively rapidly with an alcohol to form an ester and a carboxylic acid group. This allows a preponderance of monoester/monocarboxylic acid to be formed from the reaction of the cyclic anhydride with one alcohol (such as the fluorine-containing monoalcohol), followed by reaction of the remaining carboxylic acid groups with a second alcohol (such as the polyol). Alternatively, the remaining carboxylic acid groups can first be converted to the corresponding acid halide and then reacted with the second alcohol.
Representative examples of suitable dicarboxylic acids and dicarboxylic acid derivatives include the following acids and their corresponding esters, halides, and anhydrides: azelaic; maleic; fumaric; itaconic; 1,5-pent-2-enedioic; adipic; 2-methyleneadipic; 3-methylitaconic; 3,3-dimethylitaconic; sebacic; suberic; pimelic; succinic; benzylsuccinic; sulfosuccinic; gluratic; 2-methyleneglutaric; 2-sulfoglutaric; 3-sulfoglutaric; diglycolic; dilactic; 3,3xe2x80x2-(ethylenedioxy)dipropionic; dodecanedioic; 2-sulfododecanedioic; decanedioic; undecanedicarboxylic; hexadecanedicarboxylic; dimerized fatty acids (such as those obtained by the dimerization of olefinically unsaturated monocarboxylic acids containing 16 to 20 carbon atoms, for example, oleic acid and linoleic acid and the like); 1,2-, 1,4-, and 1,6-cyclohexanedicarboxylic; norbornenedicarboxylic; bi-cyclooctanedicarboxylic; and other aliphatic, heteroaliphatic, saturated alicyclic, or saturated heteroalicyclic dicarboxylic acids; and the like; and mixtures thereof. Salts (for example, alkali metal salts) of the above-described sulfonic acids can also be used.
Preferred dicarboxylic acids and dicarboxylic acid derivatives include succinic, adipic, dimer acid, azelaic acid, dodecanedioic acid, poly(ethylene glycol)diacid, poly(acrylic acid), pimelic, suberic, and sebacic acids (and derivatives thereof), and the like, and mixtures thereof; with suberic, and adipic acids (and derivatives thereof), and mixtures thereof being more preferred. Citric acid is a preferred tricarboxylic acid.
In the preparation of the polyphosphates, the hydroxyl group containing material is reacted with (poly)phosphoric acid derivatives such as dichlorophosphoric acid, tricholorphosphor oxide, and dialkyl phosphate
In the preparation of the surface treatments, the reaction product may optionally comprise at least one long chain hydrocarbon monoalcohol, monofunctional fluorochemical, water-solubilizing group containing ingredient, silane group containing ingredient, particularly in the case of polyisocyanate coreactant(s), and mixtures thereof. Alternatively, the hydroxyl group containing material, polyisocyanate, polycarboxylic acid/derivative, or phosphoric acid/derivative may be substituted to include silane groups and/or water-solubilizing groups, as previously described.
Long-chain hydrocarbon monoalcohols suitable for use in the fluoropolymer surface treatment of the present invention comprise at least one, essentially unbranched, hydrocarbon chain having from 10 to about 18 carbon atoms which may be saturated, unsaturated, or aromatic. These long-chain hydrocarbon monoalcohols can be optionally substituted, for example, with groups such as one or more chlorine, bromine, trifluoromethyl, or phenyl groups. Representative long-chain hydrocarbon monoalcohols include 1-octanol, 1-decanol, 1-dodecanol, 1-tetradecanol, 1-hexadecanol, 1-octadecanol, and the like, and mixtures thereof. Preferred long-chain hydrocarbon monoalcohols have 12 to 16 carbon atoms, with 12 to 14 carbon atoms being more preferred and 12 carbon atoms being most preferred for water solubility and performance.
Monofunctional fluorochemical compounds include those that comprise at least one Rf group. The Rf groups can contain straight chain, branched chain, or cyclic fluorinated alkylene groups or any combination thereof. The Rf groups can optionally contain one or more heteroatoms (i.e. oxygen, sulfur, and/or nitrogen) in the carbon-carbon chain so as to form a carbon-heteroatom-carbon chain (i.e. a heteroalkylene group). Fully-fluorinated groups are generally preferred, but hydrogen or chlorine atoms can also be present as substituents, provided that no more than one atom of either is present for every two carbon atoms. It is additionally preferred that any Rf group contain at least about 40% fluorine by weight, more preferably at least about 50% fluorine by weight. The terminal portion of the group is generally fully-fluorinated, preferably containing at least three fluorine atoms, e.g., CF3Oxe2x80x94, CF3CF2xe2x80x94, CF3CF2CF2xe2x80x94, (CF3)2Nxe2x80x94, (CF3)2CFxe2x80x94, SF5CF2xe2x80x94. Perfluorinated aliphatic groups (i.e., those of the formula CnF2n+1xe2x80x94) wherein n is 1 to 12 inclusive are the preferred Rf groups, with n=6 or fewer being more preferred and with n=3 to 5 being the most preferred. Further, it is preferred that the fluorochemical monofunctional compounds have a melting point above room temperature. It has been found that the oligomers derived from solid fluorochemical monofunctional compounds exhibit higher contact angle performance than lower melting compounds.
The optional water-solubilizing compounds (W-H) comprise one or more water-solubilizing groups and at least one coreactant reactive hydrogen containing group. These water solubilizing compounds include, for example, diols and monoalcohols comprising one or more water-solubilizing groups, added in addition to the one or more polyols and one or more monoalcohols as described above.
The solubilizing groups of the water solubilizing compounds include, for example, carboxylate, sulfate, sulfonate, phosphate, phosphonate, ammonium, and quaternary ammonium groups. Such groups may be represented as xe2x80x94CO2M, xe2x80x94CH2CH2)n, xe2x80x94OSO3M, xe2x80x94SO3M, xe2x80x94OPO3M, xe2x80x94PO(OM)2, xe2x80x94NR2HX, xe2x80x94NR3X, xe2x80x94NRH2X, and xe2x80x94NH3X, respectively, wherein M is H or one equivalent of a monovalent or divalent soluble cation such as sodium, potassium, calcium, and NR3H+; X is a soluble anion such as those selected from the group consisting of halide, hydroxide, carboxylate, sulfonates, and the like; and R is selected from the group consisting of a phenyl group, a cycloaliphatic group, or a straight or branched aliphatic group having from about 1 to about 12 carbon atoms. Preferably, R is a lower alkyl group having from 1 to 4 carbon atoms. The group xe2x80x94NR3X is a salt of a water-soluble acid, for example trimethyl ammonium chloride, pyridinium sulfate, etc. or an ammonium substituent. The group xe2x80x94NR2HX is the salt of a water-soluble acid, such as dimethyl ammonium acetate or propionate. The group xe2x80x94NRH2X is the salt of a water-soluble acid, such as methyl ammonium acetate or propionate. The group xe2x80x94NH3X is the salt of a water-soluble acid, such as ammonium acetate or propionate. The salt form can be made by simple neutralization of the acid group with a base such as an amine, a quaternary ammonium hydroxide, an alkali metal carbonate or hydroxide, or the like; or alternatively by simple reaction of the amino group with a carboxylic acid, a sulfonic acid, a halo acid, or the like. Carboxylic acid groups in salt form are preferred because they have been found to impart water solubility to the chemical compositions of the present invention without causing undue loss of the durable stain-release properties imparted by the chemical composition.
In the case of (poly)urethanes, the isocyanate-reactive hydrogen containing group is selected from the group consisting of xe2x80x94OH, xe2x80x94SH, NH2, and NRH wherein R is selected from the group consisting of a phenyl group, a cycloaliphatic group, or a straight or branched aliphatic group having from about 1 to about 12 carbon atoms. Preferably, R is a lower alkyl group having from 1 to 4 carbon atoms. A representative suitable diol with a solubilizing group is 1,1-bis(hydroxymethyl)propionic acid and its salts such as its ammonium salt. A representative suitable monoalcohol with a solubilizing group is glycolic acid (HOCH2COOH) and its salts. The amount of water-solubilizing group should be sufficient to solubilize the chemical composition. Typically, the isocyanate:solubilizing group ratio should be from about 3:1 to about 16:1, preferably from about 5:1 to about 11:1. Illustrative water-solubilizing compounds having suitable water-solubilizing groups include, but are not limited to, those independently selected from the group consisting of HOCH2COOH; HSCH2COOH; (HOCH2CH2)2NCH2COOH; HOC(CO2H)(CH2CO2H)2; (H2N(CH2)nCH2)2NCH3 wherein n is an integer of 1 to 3; (HOCH2)2C(CH3)COOH; (HO(CH2)nCH2)2NCH3 wherein n is an integer of 1 to 3; HOCH2CH(OH)CO2Na; N-(2-hydroxyethyl)iminodiacetic acid (HOCH2CH2N(CH2COOH)2); L-glutamic acid (H2NCH(COOH)(CH2CH2COOH)); aspartic acid (H2NCH(COOH)(CH2COOH)); glycine (H2NCH2COOH); 1,3-diamino-2-propanol-N,N,Nxe2x80x2,Nxe2x80x2-tetraacetic acid (HOCH(CH2N(CH2COOH)2)2); iminodiacetic acid (HN(CH2COOH)2); mercaptosuccinic acid (HSCH(COOH)(CH2COOH)); H2N(CH2)4CH(COOH)N(CH2COOH)2; HOCH(COOH)CH(COOH)CH2COOH; (HOCH2)2CHCH2COO)xe2x88x92(NH(CH3)3)+; CH3(CH2)2CH(OH)CH(OH)(CH2)3CO2K; H2NCH2CH2OSO3Na; H2NC2H4NHC2H4SO3H; H2NC3H6NH(CH3)C3H6SO3H; (HOC2H4)2NC3H6OSO3Na; (HOCH2CH2)2NC6H4OCH2CH2OSO2OH; N-methyl-4-(2,3-dihydroxypropoxy)pyridinium chloride, ((H2N)2C6H3SO3)xe2x88x92(NH(C2H5)3)+; dihydroxybenzoic acid; 3,4-dihydroxybenzylic acid; 3-(3,5-dihydroxyphenyl)propionic acid; salts of the above amines, carboxylic acids, and sulfonic acids; and mixtures thereof.
The optional silane groups that may be included in the synthesis of the (poly)urethanes are preferably of the following formula (I):
X1xe2x80x94R3xe2x80x94Sixe2x80x94(Y)3xe2x80x83xe2x80x83(formula II)
wherein:
X1 is xe2x80x94NH2; xe2x80x94SH; xe2x80x94OH; xe2x80x94Nxe2x95x90Cxe2x95x90O; or xe2x80x94NR4H where R4 is a phenyl, straight or branched aliphatic, alicyclic, or aliphatic ester group;
R3 is an alkylene, heteroalkylene, aralkylene, or heteroaralkylene group; and
each Y is independently a hydroxy; a hydrolyzable moiety selected from alkoxy, acyloxy, heteroalklyoxy, heteroacyloxy, halo, and oxime; or a non-hydrolyzable moiety selected from the group consisting of phenyl, alicyclic, straight-chain aliphatic, and branched-chain aliphatic, wherein at least one Y is a hydrolyzable moiety.
Representative divalent bridging radicals (R3) include, but are not limited to, those selected from the group consisting of xe2x80x94CH2CH2xe2x80x94, xe2x80x94CH2CH2CH2xe2x80x94, xe2x80x94CH2CH2CH2OCH2CH2xe2x80x94, xe2x80x94CH2CH2C6H4CH2CH2xe2x80x94, and xe2x80x94CH2CH2O(C2H4O)2CH2CH2N(CH3)CH2CH2CH2xe2x80x94.
Representative examples of hydroxy-reactive silane compounds include, but are not limited to, 3-isocyanatopropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, and the like.
The surface treatments comprising urethane linkages (e.g. polyurethanes), ester linkages (e.g. (poly)esters) or phosphate linkages can be made according to known techniques such as described in U.S. Pat. No. 3,094,547; U.S. patent application Ser. No. 09/803,708 filed Mar. 9, 2001; and U.S. patent application Ser. No. 09/804,447 filed Mar. 12, 2001.
When the surface treatment contains comprises one or more carboxylic acid groups, solubility of the composition in water can be further increased by forming a salt of the carboxylic acid group(s). Basic salt-forming compounds, such as tertiary amines, quaternary ammonium hydroxides, and inorganic bases, including, but not limited to, those selected from the group consisting of sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, and barium hydroxide, may be used in a sufficient amount (i.e., in an amount to maintain a pH of greater than about 6). These basic salt-forming compounds preferably can be added in the water phase, but optionally in the preparation of the urethane oligomers, to form salts with the incorporated, pendant and/or terminal carboxylic acid groups on the urethane oligomer. Examples of useful amine salt-forming compounds include, but are not limited to, those selected from the group consisting of ammonia, trimethylamine, triethylamine, tripropylamine, triisopropylamine, tributylamine, triethanolamine, diethanolamine, methyidiethanolamine, morpholine, N-methylmorpholine, dimethylethanolamine, and mixtures thereof. Preferred salt forming compounds include those selected from the group consisting of ammonia, trimethylamine, dimethylethanolamine, methyidiethanolamine, triethylamine, tripropylamine, and triisopropylamine, since the chemical compositions prepared therefrom are not excessively hydrophilic upon coating and curing. Since certain salts formed by the reaction of salt forming compounds, such as potassium hydroxide in combination with a carboxylic acid group, could result in undesired reaction with NCO groups, it is preferred to add the salt forming compound in a water phase after all of the diols, alcohol, and silane compounds have been reacted with the NCO groups of the polyfunctional isocyanate compound.
The fluorochemical described herein for use as surface treatment for optical elements are typically solids. The fluoropolymer(s) are combined with various solvents to form emulsion(s), solution(s) or dispersion(s). Dispersions of fluoropolymers can be prepared using conventional emulsion polymerization techniques, such as described in
The emulsion(s), solution(s), and dispersion(s) are then further diluted in order to deliver the desired concentration. It is assumed that negligible amounts of the diluted surface treatment are lost and substantially all of the surface treatment present in the emulsion, solution or dispersion is deposited on the optical elements. Hence, the concentration (ppm) based on the weight of the optical elements being coated with the emulsion, solution, or dispersion is approximately equal to the amount retained on the optical elements upon evaporation of the solvent. Although aqueous emulsions, solutions, and dispersions are preferred, up to about 50% of a cosolvent such as ethanol, methanol, ethyl acetate, n-methyl pyrrolidone, isopropanol, or methyl perfluorobutyl ether may be added. Preferably, the aqueous emulsions, solutions, and dispersions comprise less than about 30% cosolvent, more preferably less than about 10% cosolvent, and most preferably the aqueous emulsions, solutions, and dispersions are substantially free of cosolvent. The aqueous surface treatment is coated on the optical elements typically by combining the optical elements with the minimum volume of aqueous surface treatment to uniformly coat the optical elements and then drying the coated elements. Although aqueous delivery is preferred, the surface treatment could also be applied from 100% organic solvent as well as by other techniques such as vapor deposition.
The amount of fluoropolymer surface treatment employed for coating the optical elements typically ranges from about 5 ppm to about 1000 ppm with respect to the weight of the optical elements. A preferred fluorochemical compound is one that contributes the desired floatation at minimum concentrations. The amount of fluorochemical derivative is usually about 600 ppm or less, preferably about 300 ppm or less, more preferably about 150 ppm, even more preferably about 100 ppm, and most preferably about 50 ppm or less. Typically, the overall coating thickness of the surface treatment of the present invention is greater than about 15 Angstroms, preferably, greater than about 20 Angstroms, and more preferably, greater than about 50 Angstroms. Thicker coatings can be obtained if desired, although it is preferred that the coating thickness be no greater than about 500 Angstroms, more preferably, no greater than about 300 Angstroms, and most preferably, no greater than about 150 Angstroms thick. Excessive concentrations of surface treatment can result in agglomeration of the optical elements. Such limits can be determined by routine experimentation and in some instances the agglomeration can be reduced by the use of flow control agents.
The surface treatment may comprise any one of fluorochemicals described herein, various blends of such fluorochemicals, as well blends of such fluorochemicals with other surface treatments. Accordingly, the optical elements may comprise one or more additional surface treatments such as adhesion promoters and flow control agents that reduce particle agglomeration. Various silanes such as 3-aminopropyltriethoxysilane are commonly employed as adhesion promoters, whereas methacrylato chromic chloride, commercially available from Zaclon Inc, Cleveland, Ohio under the trade designation xe2x80x9cVolanxe2x80x9d is a typical flow control agent.
The surface treated optical elements of the invention can be employed for producing a variety of reflective products or articles such as pavement markings, retroreflective sheeting, and beaded projection screens. Such products share the common feature of comprising a liquid binder layer and embedding a multitude of optical elements into the binder surface followed by solidifying the binder to retain the optical elements in place. In the pavement markings, retroreflective sheeting, and beaded projection screens of the invention, at least a portion of the optical elements will comprise the surface treated optical elements of the invention. Typically, the majority of, and preferably substantially all, the optical elements employed in the manufacture of the reflective products will comprise the surface treated optical elements of the invention.
Various known binder materials may be employed including various one and two-part curable binders, as well as thermoplastic binders wherein the binder attains a liquid state via heating until molten. Common binder materials include polyacrylates, methacrylates, polyolefins, polyurethanes, polyepoxide resins, phenolic resins, and polyesters. For reflective paints the binder may comprise reflective pigment. For reflective sheeting, however, the binder is typically transparent. Transparent binders are applied to a reflective base or may be applied to a release-coated support, from which after solidification of the binder, the beaded film is stripped and may subsequently be applied to a reflective base or be given a reflective coating or plating.
There are several types of retroreflective articles in which the surface treated optical elements may be used such as exposed lens (e.g. U.S. Pat. Nos. 2,326,634 and 2,354,018), embedded lens (e.g. U.S. Pat. No. 2,407,680), and encapsulated lens (e.g. U.S. Pat. No. 4,025,159) retroreflective sheeting. Retroreflective articles can be prepared by known methods including a method comprising the steps of: (i) forming a top coat on a release coated web (e.g. coating a solution of hydroxy-functional acrylic polyol and aliphatic polyfuntional isocyanate onto a release-coated paper web and then curing by conveying the coating through an oven at about 150xc2x0 C. for about 10 minutes); (ii) coating the exposed surface of the top coat with a liquid binder (e.g. coating a solution comprising an oil-free synthetic polyester resin and a butylated melamine resin); (iii) drying the binder to form an uncured tacky bead-bond layer; (iv) cascade-coating onto the bead-bond layer a plurality of glass microspheres forming a monolayer of embedded glass microspheres; (v) curing the bead-containing bead-bond layer to a non-tacky state (e.g. by heating to 150xc2x0 C.); forming a space coat layer over the bead-containing bead-bond layer (e.g. coating a 25% solids solution comprised of a polyvinylbutyral resin and a butylated melamine resin in a solvent and curing at 170xc2x0 C. for about 10 minutes); (vi) applying a reflective layer over the space coat layer (e.g. vapor deposition of aluminum metal at a thickness of about 100 nm); and stripping away the release-coated web. An adhesive layer is typically applied to the reflective layer (e.g. by coating a 0.025 mm thick layer of an aggressive acrylic pressure-sensitive adhesive onto a silicone-treated release liner and pressing the adhesive against the reflective layer).
The surface treated optical elements are also useful in pavement marking materials. The optical elements can be incorporated into coating compositions that generally comprise a film-forming material having a multiplicity of optical elements dispersed therein. The surface treated optical elements may also be used in drop-on applications for such purposes as highway lane striping in which the optical elements are simply dropped onto wet paint or hot thermoplastic and adhered thereto.
One typical pavement marking sheet is described in U.S. Pat. No. 4,248,932. This sheet material is a prefabricated strip adapted to be laid on and secured to pavement for such purposes as lane dividing lines and comprises a base sheet, such as a soft aluminum foil which is conformable to a roadway surface; a top layer (also called the support film or binder film) adhered to one surface of the base sheet and being very flexible and resistant to rupture; and a monolayer of surface treated optical elements such as transparent microsphere lens elements partially embedded in the top layer in a scattered or randomly separated manner. The pavement marking sheet construction may also include an adhesive (e.g., pressure sensitive, heat or solvent activated, or contact adhesive) on the bottom of the base sheet. The base sheet may be made of an elastomer such as acrylonitrile-butadiene polymer, polyurethane, or neoprene rubber. The top layer in which the surface treated microspheres are embedded is typically a polymer such as vinyl polymers, polyurethanes, epoxies, and polyesters. Alternatively, the surface treated microsphere lenses may be completely embedded in a layer of the pavement marking sheet.
Pavement marking sheets may be made by processes known in the art (see e.g. U.S. Pat. No. 4,248,932), one example comprising the steps of: (i) coating onto a base sheet of soft aluminum (50 micrometers thick) a mixture of resins (e.g., epoxy and acrylonitrile butadiene elastomer mixture), pigment (TiO2) and solvent (e.g., methyl ethyl ketone) to form the support film; (ii) dropping onto the wet surface of the support film ingredients a multiplicity of the surface treated optical elements of the invention; and curing the support film at 150xc2x0 C. for about 10 minutes. A layer of adhesive is then usually coated on the bottom of the base sheet.
Pigments or other coloring agents may be included in the top layer in an amount sufficient to color the sheet material for use as a traffic control marking. Titanium dioxide will typically be used for obtaining a white color; whereas, lead chromate will typically be used to provide a yellow color.
A rear projection screen is a sheet-like optical device having a relatively thin viewing layer that is placed at an image surface of an optical projection apparatus. Rear projection screen displays comprising glass microspheres embedded in an opaque matrix are known from U.S. Pat. No. 2,378,252, for example. Generally, the size of the microspheres is less than about 150 microns. For maximum brightness, the microspheres have an index of refraction of less than about 1.8 and preferably from about 1.45 to about 1.75. A plurality of the surface treated glass microspheres are attached to and are in intimate contact with a major surface of a transparent substrate. Alternatively, a diffusion layer can be formed by coating an optically inhomogeneous material as a separate layer onto the transparent substrate prior to application of the opaque binder and microspheres. Rear projection screens are prepared by i) providing a substrate (e.g. polyester, polycarbonate) having an opaque binder disposed thereon (e.g. acrylate loaded with carbon black to make it opaque); and ii) applying the surface treated glass microspheres under conditions effective to produce microspheres in optical contact with the substrate and embedded in the opaque matrix.
In some useful embodiments of the invention, a specular reflective means is provided by a layer of metal (e.g. aluminum) vapor-deposited on the surface treated microspheres. Another useful specular reflective means is a dielectric reflector which comprises one or more layers of a transparent material behind the microspheres, each layer having a refractive index of about 0.3 higher or lower than that of the adjacent layer or beads and each layer having an optical thickness corresponding to an odd numbered multiple of about 1/4 wavelength of light in the visible range. More detail on such dielectric reflectors is found in U.S. Pat. No. 3,700,305.